Selective extraction of hemicelluloses from spruce using switchable ionic liquids (original) (raw)
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Comptes Rendus Biologies, 2004
Lignin in kraft pulp was extracted by enzymatic hydrolysis of the carbohydrates, acidolysis with dioxane-water-HCl (conventional method), and acidolysis with acetic acid-water-ZnCl 2. The latter method was shown to extract lignin with a better yield than for conventional acidolysis and with a much lower content in impurities than for enzymatic hydrolysis. It was confirmed by 13 C NMR analysis of the lignin samples that conventional hydrolysis modified the lignin polymer, causing the cleavage of some aryl-ether linkages. The cleavage was also observed on a model compound submitted to the same extraction conditions. In that respect, the acetic acid-water-ZnCl 2 method was less damaging and consequently more suitable for analytical purposes. To cite this article: D. Lachenal et al., C. R. Biologies 327 (2004). 2004 Published by Elsevier SAS on behalf of Académie des sciences. Résumé Extraction de lignine résiduelle de pâtes de résineux de type kraft : avantages de la méthode d'acidolyse à l'acide acétique. Les lignines présentes dans les pâtes kraft ont été extraites après hydrolyse enzymatique des polysaccharides, acidolyse par le dioxane aqueux-HCl (méthode conventionnelle) et acidolyse par un mélange d'acide acétique-eau, en présence de ZnCl 2. Cette dernière méthode a permis d'extraire les lignines des fibres avec un meilleur rendement que dans la procédure classique d'acidolyse, et avec beaucoup moins d'impuretés qu'après une hydrolyse enzymatique. Il a été confirmé par RMN 13 C des lignines que l'acidolyse conventionnelle modifiait les lignines en rompant quelques liaisons de type aryl-éther. Ces ruptures ont également été observées sur des modèles moléculaires soumis au même protocole d'extraction. La combinaison ✩ Many thanks to Bernard Monties for the enthusiasm he has been able to transmit to us and for his immense knowledge of the state-of-the art in wood chemistry, from which we all benefited.
2009
Lignin was extracted from different softwood and hardwood materials using sodium xylenesulphonate (SXS) solution as a solvent. Extracted lignin was precipitated from the solvents, washed and freeze-dried. The obtained lignin samples were analysed for purity using FT-IR (Fourier Transform Infrared Spectroscopy) and acid methanolysis-GC (Gas Chromatography ) was used for determining the possible traces of carbohydrates in the extracted lignin samples. Chemical analysis was also done for the extracted wood materials. The extraction yield of lignin varied from 20% to 70% depending of the type of wood material. It was suggested that the degree of delignification was due to topochemistry of lignin and wood capillary structure. The different lignin samples contained only small amounts of residual carbohydrates and no traces of sodium xylenesulphonate were found after precipitating and washing. We also suggested that SXS was an attractive alternative as a green solvent for extraction of a l...
Highly efficient single-step pretreatment to remove lignin and hemicellulose from softwood
Bioresources, 2019
The use of lignocellulosic softwood residues as feedstock for the production of bioethanol and other value-added chemical products has been limited by its high recalcitrance. Alkaline or organosolvent pretreatments have been used to remove recalcitrance in softwoods. Although these methods partially remove lignin and hemicellulose, they also result in low glucose recovery. In the first case, there is low cellulose hydrolizability, and in the second, there is a loss of cellulose. This study evaluated both methods combined into one step: alkaline hydrolysis of the biomass in the presence of an organosolvent. Different conditions of temperature and residence times were assayed. The efficiency of these conditions was quantified as the percentage of lignin and hemicellulose removed from the biomass without loss of cellulose. The substrate produced with the most efficient conditions removed 91% of the lignin and 89.1% of the hemicellulose with no loss of cellulose. Enzymatic hydrolysis of this biomass was 90% to 95%, with a substrate concentration of 3% and with five filter paper units per gram of cellulose (FPU/g cellulose). These results indicated that this one-step alkaline-organsolvent process, applied as a pretreatment to softwood, allows highly efficient lignin and hemicellulose removal. 100% of cellulose was recovered, and there was between 90 and 95% glucose yield after enzymatic digestion.
A method for isolation of milled-wood lignin involving solvent swelling prior to enzyme treatment
Wood Science and Technology, 1995
A new lignin isolation method has been developed. Wood and pulp were subjected to ball milling, swelled in an organic solvent, and then treated with a cellulase. The enzyme digestion time could be shortened to 1 day with this method. The lignin obtained has been named Swelled Enzyme Lignin (SEL). Swelling and enzyme digestion conditions and their effects on lignins
Toward a Better Understanding of the Lignin Isolation Process from Wood
Journal of Agricultural and Food Chemistry, 2006
The recently developed protocol for isolating enzymatic mild acidolysis lignins (EMAL) coupled with the novel combination of derivatization followed by reductive cleavage (DFRC) and quantitative 31 P NMR spectroscopy were used to better understand the lignin isolation process from wood. The EMAL protocol is shown to offer access at lignin samples that are more representative of the overall lignin present in milled wood. The combination of DFRC/ 31 P NMR provided a detailed picture on the effects of the isolation conditions on the lignin structure. More specifically, we have used vibratory and ball milling as the two methods of wood pulverization and have compared their effects on the lignin structures and molecular weights. Vibratory-milling conditions cause substantial lignin depolymerization. Lignin depolymerization occurs via the cleavage of uncondensed -aryl ether linkages, while condensed -aryl ethers and dibenzodioxocins were found to be resistant to such mechanical action. Condensation and side chain oxidations were induced mechanochemically under vibratory-milling conditions as evidenced by the increased amounts of condensed phenolic hydroxyl and carboxylic acid groups. Alternatively, the mild mechanical treatment offered by ball milling was found not to affect the isolated lignin macromolecular structure. However, the overall lignin yields were found to be compromised when the mechanical action was less intense, necessitating longer milling times under ball-milling conditions. As compared to other lignin preparations isolated from the same batch of milled wood, the yield of EMAL was about four times greater than the corresponding milled wood lignin (MWL) and about two times greater as compared to cellulolytic enzyme lignin (CEL). Molecular weight distribution analyses also pointed out that the EMAL protocol allows the isolation of lignin fractions that are not accessed by any other lignin isolation procedures.
Holzforschung, 2014
Various lignin determination methods have been applied to hemicellulose-rich wood extracts obtained after pressurized hot-water extraction (PHWE) and membrane ultrafiltration (UF). In focus were the chlorine number (Cl no.) method, the acetyl bromide method, and the four modifications of the Klason lignin determination, such as the KCL, TAPPI, LAP, and Goldschmid methods. The furfural (F) and hydroxymethylfurfural (HMF) concentrations in the acid hydrolysates were also determined. The mass balances of the fraction were calculated with respect to the contents of dry solids and lignin, including the acid-soluble lignin. The reliability of the methods was evaluated based on the lignin mass balances and the gross chemical composition of the extracts. Although the results were dependent on the method applied, the lignin mass balance calculations yielded similar results in general.
Continuous Countercurrent Extraction of Hemicellulose from Pretreated Wood Residues
Applied Biochemistry and Biotechnology, 2001
Two-stage dilute acid pretreatment followed by enzymatic cellulose hydrolysis is an effective method for obtaining high sugar yields from wood residues such as softwood forest thinnings. In the first-stage hydrolysis step, most of the hemicellulose is solubilized using relatively mild conditions. The soluble hemicellulosic sugars are recovered from the hydrolysate slurry by washing with water. The washed solids are then subjected to more severe hydrolysis conditions to hydrolyze approx 50% of the cellulose to glucose. The remaining cellulose can further be hydrolyzed with cellulase enzyme. Our process simulation indicates that the amount of water used in the hemicellulose recovery step has a significant impact on the cost of ethanol production. It is important to keep water usage as low as possible while maintaining relatively high recovery of soluble sugars. To achieve this objective, a prototype pilot-scale continuous countercurrent screw extractor was evaluated for the recovery of hemicellulose from pretreated forest thinnings. Using the 274-cm (9-ft) long extractor, solubles recoveries of 98, 91, and 77% were obtained with liquid-to-insoluble solids (L/IS) ratios of 5.6, 3.4, and 2.1, respectively. An empirical equation was developed to predict the performance of the screw extractor. This equation predicts that soluble sugar recovery above 95% can be obtained with an L/IS ratio as low as 3.0.
Lignin extraction from biomass with protic ionic liquids
Green Chemistry
A highly effective method has been developed for the simple extraction of lignin from lignocellulosic biomass using a potentially inexpensive protic ionic liquid (PIL). After the lignin-extraction step, the PIL is easily recovered using distillation leaving the separated lignin and cellulose-rich residues available for further processing. Biopolymer solubility tests indicate that increasing the xylan (i.e., hemicellulose) solubility in the PIL results in greater fiber disruption/penetration, which significantly enhances the effectiveness of the lignin extraction.
An improved procedure for isolation of residual lignins from hardwood kraft pulps
Holzforschung, 2000
Residual lignin preparations were isolated from birch, aspen and Eucalyptus grandis kraft pulp by enzymatic hydrolysis of the pulps with cellulase:hemicellulase mixture. Residual lignin preparations were characterized by investigation of nitrogen content, carbohydrate composition and molecular mass distribution. The use of enzyme with high activity and optimization of enzyme charge resulted in significant decrease in protein contaminants in residual lignin preparations as compared to previously published results. A second order law correlation between enzyme mass charge and nitrogen content in birch residual lignin preparations indicates a strong effect of enzyme charge on the amount of protein contaminants. However, the enzyme charge in the range studied does not appreciably affect either the yields of the residual lignin preparations or percentage and composition of carbohydrates in these preparations. The optimal enzyme charge was highest for Eucalyptus grandis pulp and lowest for birch pulp. It has been suggested that a significant part of the hardwood residual lignin in pulps, especially in E. grandis pulp, consists of low molecular mass lignin fragments bonded to pulp carbohydrates. Higher amount of glucose in E. grandis residual lignin preparation compared to those from birch and aspen implied a higher frequency of lignin-cellulose bonds in eucalypt pulp. Different fractions of birch residual lignin have rather similar molecular mass distribution, which was not affected by the charge of the enzyme. Eucalypt residual lignin preparation had higher molecular mass than birch residual lignin. a This paper was partially present at the 7 th Brazilian Symposium on the Chemistry of Lignin and Other Wood Components, Belo Horizonte, MG, Brazil, 2001. pp. 61-68. Isolation of hardwood residual lignins 465